To prevent a piston pin attached to a piston from coming off, a C-shaped clip is fitted into an annular groove of a hole into which the piston pin is installed. A device for automatically conducting such a C-shaped clip fitting operation is proposed in Patent Document 1. The device comprises an ejecting cylinder, a positioning cylinder, and a fitting cylinder, wherein a C-shaped clip held within a holder is pushed slantwise in a cylindrical member in a reduced diameter condition by the ejecting cylinder, the cylindrical member is caused to come down by the positioning cylinder to touch a piston, and the clip is caused to engage the inside of an annular groove by the fitting cylinder.
Devices for separating workpieces other than the C-shaped clips one by one disclosed in Patent Documents 2 and 3 are also known.
The device disclosed in Patent Document 2 is provided in such a manner that a cylinder containing a workpiece is arranged slantwise, a spiral bar adapted to rotate by a motor is provided within the cylinder, and the workpieces are supplied one by one from an upper opening of the cylinder as the spiral bar rotates.
The device disclosed in Patent Document 3 is provided in such a manner that a slider is disposed slantwise, a stopper is disposed on the lower end of the slider, and workpieces slipping off the slider are separated one by one by the stopper.
[Patent Document 1] Japanese Patent Application Publication No. 9-225754
[Patent Document 2] Japanese Patent Application Publication No. 9-135099
[Patent Document 3] Japanese Patent Application Publication No. 2003-175425
A circular workpiece such as a C-shaped clip and a piston ring is usually narrow and thin. Further, oil and rust retardant are often attached to the workpiece. In the case of a cartridge and the like in which a number of circular workpieces are bundled, the circular workpieces cling to one another and separation of the workpieces by the devices stated above is quite difficult.